1. Field of the Invention
The present invention relates to a molding composition or material which is suitable for use as a lamp reflector, more particularly, a molding composition suitable for use as a lamp reflector in headlamps, fog lamps, and other lamps provided in automobiles, as well as a process for producing a lamp reflector using the molding composition, and a lamp reflector.
2. Description of the Related Art
Since lamps, particularly headlamps, fog lamps and other lamps, use very high intensity bulbs, reflectors for these lamps must withstand the intense heat emitted from filaments during use of the lamps. For this reason, substrates for reflectors are formed of thermosetting resins, and unsaturated polyester molding compositions have conventionally been used for this purpose.
For example, a conventional reflector composition comprises a thermosetting unsaturated polyester, 12 to 18% by weight glass fiber and, incorporated into the molding composition, a filler, such as calcium carbonate, a fatty acid ester which acts as a compatible release agent, and an aliphatic peroxy compound which acts as a curing catalyst.
High heat resistance, enough to withstand the temperature (about 180.degree. C.) of heat emitted when the lamp is in an "on" state, is required of the unsaturated polyester resin used in the lamp reflector. The use of the conventional polyester molding composition as a substrate material for a lamp reflector, however, results in thermal deformation of the lamp reflector due to the increase in temperature within a lamp chamber of the lamp when the lamp is in an "on" state. Further, it has been found that shrinkage during thermal curing at the time of injection molding of the lamp reflector causes shrinkage of the substrate, which deteriorates the dimensional stability and surface smoothness of the reflector. This, in turn, creates strain on the surface of the reflector, and the strain renders the surface of the reflector uneven, making it difficult to accurately control light emitted from the bulb. Consequently, problems occur including that drivers of oncoming cars are "dazzled" by the glare of the light emitted from the lamp, and light distribution standards cannot be satisfied.
Since this type of reflector for a high intensity lamp should have a highly accurate reflecting surface which is free from optical aberrations, it is necessary to develop a thermosetting plastic molding material which can be used as a substrate for a reflector, the material having excellent heat resistance, dimensional stability, surface smoothness and strength.